Motor driven tool such as a pole hedge trimmer with a locking mechanism for the turnable cutting unit

ABSTRACT

This invention relates to a motor driven tool such as a pole hedge trimmer, a pole saw or the like comprising a drive unit ( 11 ) that via a shaft tube ( 12 ) enclosing a drive shaft and being provided with a handle ( 16 ), is connected to a cutting unit ( 13 ) which is turnably secured to the shaft tube. The turnable connection is under the influence of a locking mechanism (L) which from the normal working position of the operator can be released by means of a control means (M) arranged at a distance from the locking mechanism (L) and close to the handle ( 16 ).

This invention relates to a motor driven tool such as a pole hedgetrimmer, a pole saw or the like comprising a drive unit that via a shafttube is connected to a cutting unit which is turnably secured to theshaft tube.

Hedge trimmers and saws of the type mentioned above are provided withshaft tubes of different lengths and are used for trimming small as wellas large trees, hedges, bushes and the like. These tools, that areprovided with a handle having necessary control means for operating thedrive unit and a further handle placed at the shaft tube, make itpossible to find a comfortable working position when trimming bushes andtrees and hedges since i.a. the cutting unit can be turned with respectto the shaft tube. This means that the operator before the work startscan put the cutting unit in a suitable angular position in order toadapt the severing or cutting means to the working position of theoperator. However, the tools of today are designed such that theadjustment means are placed in close vicinity of the cutting unit. Thismeans that adjustment operation is complicated since the operator isforced to leave hold of one or both handles in order to reach thelocking means. Then the cutting unit has to be turned by means of aspecial handle before it is locked in its new position. The lockingmeans and the special handle are usually also placed such that there isa risk that the operator gets injured by the cutting or severing partsof the cutting unit.

It is also previously known, see U.S. Pat. No. 4,651,420, to provide apole cutter with an angle adjustment means for the cutter unit. Thecutter unit is driven by the reciprocating motion of a Bowden cable andthe adjustment means comprises a pivotable handle that via a rod isconnected to the cutter unit support. The handle can be locked indifferent position by means of a teethed latch. This arrangement ishowever very poor and is not acceptable from a safety point of viewsince the latch can easily disengage from the handle which would causethe cutter unit to move uncontrolled. Moreover to change the angularposition of the cutter unit the operator has to turn off the engine andmove one of his hands from the grip to the latch to choose a newposition for the latch before starting the engine again.

The purpose of this invention is to create an arrangement simplifyingthe adjustment procedure whereby the operator can turn the cutting unitwith respect to the shaft tube mainly with preserved grip about thehandle parts. This is achieved by means of a device having thecharacteristics mentioned in the claims.

Several embodiments of the invention will now be described withreference to the accompanying drawings on which

FIG. 1 is a perspective view of a pole hedge trimmer of the type inquestion,

FIG. 2 is a perspective view of a first embodiment of the adjustingarrangement,

FIG. 3 is a section through a part of the arrangement shown in FIG. 2,

FIG. 4 is a section through another part of the arrangement shown inFIG. 2,

FIG. 5 is a perspective view of a second embodiment of the adjustmentarrangement,

FIG. 6 is a side view of the locking arrangement shown in FIG. 5,

FIG. 7 is a section on the line VII-VII in FIG. 6 whereas

FIG. 8 is a further embodiment of the locking mechanism.

As appears form FIG. 1 the pole hedge cutter comprises a drive unit 11which via a shaft tube 12 is connected to a cutting unit 13. The driveunit 11 can be of any type such as an internal combustion engine or anelectric motor whose output shaft is connected to a drive shaft, notshown, that is placed within the shaft tube and that via a gear 14 isconnected to the cutting unit. The shaft tube 12 has an inner handle 15that is provided with throttle control means and additional controlmeans for the drive unit and an outer handle 16 designed as a sleeve ofgrip friendly material. The cutting unit 13 in a conventional manner isprovided with stationary, comb shaped knive protectors co-operating withcorresponding knives arranged to move forwards/backwards and beingdriven by the drive shaft via the gear 14. The cutting unit 13 is bymeans of a turnable connection A supported by the shaft tube 12. Theturnable connection comprises a braking and locking means L that can bereleased by means of a control means M arranged close to the outerhandle.

According to the embodiment shown in FIG. 2 the control means Mcomprises a turnable handle designed as a sleeve 17 and arranged outsidethe shaft tube 12 close to the outer handle 16. The sleeve 17 thatpreferably is provided with an outer shell of grip friendly material isat one of its end provided with an outer gear rim 18, see FIG. 3,co-operating with a tube socket 19 provided with a gear rim engaging thegear rim 18. The tube socket 19 is turnably supported in a gear box 20surrounding the gear mechanism. The tube socket 19 drives a turning rod21 having one end which is wave shaped and slideably arranged in apocket of the tube socket 19 such that the turning rod follows theturning motion of the gear wheel at the same time as it has thepossibility to move in the axial direction. The other end 23 of theturning rod is threaded and inserted into a lug 24 serving as a nut atthe turnable connection A. The end part of the turning rod that extendsfrom the lug is arranged to act on a lever 25 which is a part of thelocking mechanism L. The lever 25 is supported for turning motion abouta stub shaft 26 and has an abutment surface 27 resting against one endof a sleeve 28 whose other end rests against a shoulder 29 which is apart of a clamp connection arranged at the bearing housing andcomprising a clamping ring 30 surrounding a turning shaft, not shown, ofthe cutting unit. The clamping ring 30 also comprises a shoulder 31 inwhich a screw 32 is threaded the screw being freely movable in a throughhole in the shoulder 29 and being provided with a screw head 33 which isplaced in the sleeve 28. Between the screw head 33 and the shoulder 29there are several spring washers 34. In order to prevent branches fromgetting entangled between the shaft tube 12 and the turning rod 21 it iscovered by a protecting shell 35 which is secured to the shaft tube.

The arrangement shown in FIG. 2-4 operates in the following manner. Whenthe operator desires to change the position of the cutting unit thesleeve 17 is turned which means that the tube socket 19 follows themotion and acts on the turning rod such that it by means of its threadedengagement with the lug 24 is moved axially to the left in FIG. 4 andhence influences the lever 25. This means that the lever is turnedclockwise about the stub shaft 26 until the abutting surface 27 does notabut the sleeve 28 any longer which means that the shoulder 29 moves tothe left in the figure such that the clamp ring 30 looses its grip aboutthe turning shaft of the cutting unit. Because of the force created bythe screw 32 and the spring washers 34 on the shoulder 29 a certain gripabout the turning shaft is maintained. By pressing the cutting unit 13against the ground or some other kind of counter acting object, therebyovercoming the braking moment that the spring washers create, the angleof the cutting unit with respect to the shaft tube 12 can now bechanged. Then the cutting unit 13 is locked by turning the sleeve 17 inthe opposite direction which means that the lever 25 will press thesleeve 28 against the shoulder 29 such that the distance between the twoshoulders 29, 31 decreases thereby locking the clamping ring 30 aboutthe turning shaft of the cutting unit.

At the embodiment shown in FIG. 5-7 the control means M comprises an arm39 which by means of a shaft 40 is turnably supported between two sidewalls 41 arranged on the shaft tube 41. The shaft 40 supports a pocket,not shown, which in the same manner as has been mentioned at theembodiments described above encloses one end of a turning rod 42 suchthat it can be moved axially at the same time as it is turned. The otherend of the turning rod is threaded and inserted into a central, tubeshaped, threaded opening 43 arranged in a screw 44 which is threadedinto a bearing housing 45 surrounding the turning shaft, not shown, ofthe cutting unit. The bearing housing 45 is provided with a recess 46directed towards the turning shaft and comprising a brake pad 47 movablein the radial direction. Between the brake pad 47 and the inner end ofthe screw 44 there are several spring washers 48 having a centralopening in which the turning rod 42 is freely movable and arranged suchthat it abuts the brake pad 47.

The arrangement shown in FIG. 5-7 operates in the following manner. Inorder to adjust the angle of the cutting unit 13 with respect to theshaft tube 12 the arm 39 is acted on whereby the turning motion istransferred to the turning rod 42. This means that the turning rod bymeans of the engagement with the screw 44, which is stationary arrangedin the brake drum, is moved axially towards the left in FIG. 7 such thatthe grip from the brake pad 47 on the cutting unit turning shaft, whichis inserted in the surrounding bearing housing 45, ceases. Because ofthe spring force created by the spring washers on the brake pad 47 acertain braking moment on the turning shaft of the cutting unit isretained. This means that the operator can then push the cutting unitagainst a suitable counter acting object for instance the ground, inorder to achieve a force by means of which the cutting unit can beturned with respect to the shaft tube. In order to lock the cutting unitin the new position the aim 39 is moved back to its original positionwhich means that the turning rod will move towards the right in FIG. 6and thereby push the brake pad 47 against the turning shaft. In order toset a suitable braking moment when the locking function is not activatedthe screw 44 can be turned such that the force created by the springwashers 48 against the brake pad 47 is changed in a suitable way.

The embodiment of the locking mechanism L shown in FIG. 8, in the samemanner as in the embodiments previously described, comprise a turningrod 50 which is influenced by a control means the end of the turning rodextending through a threaded through opening 51 of one of two legs 52,53 of a U-shaped clamp shoe 54. The clamp shoe 57 partly surrounds twoshoulders 55, 56 of a clamp ring 57 arranged on a bearing housing theclamp ring surrounding the turning shaft, not shown, of the cuttingunit. The clamp shoe 57 has a slot 58 separating the two shoulders 55,56 which are each provided with a through hole 59, 60 that are coaxialwith the hole 51. The hole 59 is threaded and supports a screw 61 havingone end abutting the end of the turning rod 50 and being partly threadedinto the hole 59 whereas the screw runs freely through the hole 60.Further there are several spring washers 62 surrounding the screw 61 andplaced between the shoulder 56 and the head 63 of the screw 61.

The locking mechanism described in FIG. 8, which might be used togetherwith anyone of the control means M being previously described, operatesin the following manner. When the locking function is to be loosed thecontrol means is actuated such that the turning rod 59 becomes a turningmotion which means that the turning rod because of the threadedengagement with the leg 52 of the clamp shoe 54 is moved towards theleft in FIG. 8 with respect to the clamp shoe 54 such that the end ofthe turning rod 50 which is freely movable in the opening 59 disengagesthe end of the screw 61. This means that the force which is transferredfrom the clamp shoe 54 via the leg 53 to the screw head 63 ceases suchthat the locking effect disappears at the same time as a certain gripremains between the turning shaft of the cutting unit and the bearinghousing because of the clamping force created by the spring washers 62.The operator can then change the angle of the cutting unit 13 withrespect to the shaft tube in a manner described previously after whichthe control means is influenced to again lock the cutting unit in thenew position.

It should in this connection be pointed out that the combination of thecontrol means M and the locking means L which has been shown in theembodiments is solely illustrative and that it of course is possible touse them in any combination. It should also be stressed that even if theembodiments mentioned above relate to hedge trimmers the describedarrangements are applicable also for similar types of tools such as forpole saws (i.e. saws on which a guide plate with a saw chain is arrangedat the upper part of the shaft tube and a drive unit is arranged at thelower part of the shaft tube) clearing saws and trimmers having cuttingunits with saw blades and cutting filaments.

1. Motor driven tool such as a pole hedge trimmer, a pole saw or thelike comprising a drive unit (11) that via a shaft tube (12) enclosing adrive shaft and being provided with a handle (16), is connected to acutting unit (13) which is turnably secured to the shaft tube,characterized in that the turnable connection is under the influence ofa locking mechanism (L) which from the normal working position of theoperator can be released by means of a control means (M) arranged at adistance from the locking mechanism (L) and close to the handle (16). 2.Tool according to claim 1 characterized in that the locking mechanism(L) is connected to a rod (21,42,50) which is mainly parallel to theshaft tube and by means of which a turning or forward/backwards movementis transferred from the control means (M) to a locking means being apart of the locking mechanism (L) possibly via a gear transmission. 3.Tool according to claim 2 characterized in that the locking mechanism(L) comprises a brake mechanism which by means of a force creating means(34,48,62) in the non locked position of the cutting unit (13) creates abraking force against outer forces that influences the cutting unit. 4.Tool according to claim 2 characterized in that the control means (M)comprises a turnable sleeve (17) surrounding the shaft tube or a lever(39) turnably arranged at the shaft tube and being directly orindirectly connected to the rod (21,42,50).
 5. Tool according to claim 1characterized in that the locking mechanism (L) comprises a clamp means.6. Tool according to claim 5 characterized in that the clamp meanscompletely or partly surrounds a shaft around which the cutting unit isturnable.
 7. Tool according to claim 6 characterized in that the clampmeans comprises a clamp ring (30) having two shoulders (29,31) or thelike being under the influence of a spring loaded screw connection (32)one of the shoulders (29) being movable towards the other shoulder (31)by means of a lever (25) arranged to be acted on by the control means(M) via a turning rod (23).
 8. Tool according to claim 6 characterizedin that the clamp means comprises a bearing housing (45) taking up saidshaft and enclosing a brake pad (47) which is acted on by a turning rod(42) in order to lock the shaft in the bearing housing the brake padbeing under the influence of a spring means (48).
 9. Tool according toclaim 7 characterized in that the spring characteristics of the springmeans (48) is adjustable by means of a sleeve (44) which is threadedinto the bearing housing (45) and having a through, threaded opening(43) through which the turning rod (42) extends and abuts the brake pad(47).
 10. Tool according to claim 6 characterized in that the clampmeans comprises a clamp ring (57) enclosing the shaft and having twoshoulders (55,56) which are partly surrounded by a U-shaped clamp shoe(54) having one leg (52) with a through opening (51) through which athreaded turning rod (50) is inserted the opening being coaxial with athrough opening (59,60) in each shoulder (55,56) and receiving to aspring loaded screw (60) arranged to be influenced by the other leg (53)the end of the screw (60) normally abutting the end of the turning rod(50).